75hp missing after high speed runs

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Namtack1

Recruit
Joined
Jan 7, 2004
Messages
5
I have 2ea. 1996 3 cyl. 75hp mercury outboard engines. One was filled with mud and burned up a piston. The other was leaking water from about 6 places around the block and center spark plug area. I took it apart and it was surprisingly free of mud and fairly clean. I marinetexed the holes and reassembled it. Now,it idles fine and just above an idle in gear,works just fine. At high speeds it is very powerful. When back down to very low speed, it shakes like is it missing on one cylinder. After a while,it runs just fine again. Even with all this shaking it continues to run and will go right back to high speed if called on. What to look for in this engine. Any reputable companies selling powerheads? Thanks
 
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Mod2

Senior Chief Petty Officer
Joined
Jun 19, 2003
Messages
713
Re: 75hp missing after high speed runs

Welcome to iboats forums Doug...I'm going to move your post over to Mercury/Mariner Repair forum. You'll get quicker help there.
 
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dilligafda

Petty Officer 1st Class
Joined
May 13, 2003
Messages
315
Re: 75hp missing after high speed runs

Setting the top carb 1/4 turn out and the others 1 1/4 turns out is an old trick used by techs to get the idle to smooth out. Something I have been doing for a few years. For whatever reason, when the carbs are all set at 1 1/4 turn out, the fuel recirculation system overloads the top cylinder and causes a rough idle. With the top carb at 1/4 turn out, it allows wenough fule for lubrication and the recirc system provides the rest.
 
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Namtack1

Recruit
Joined
Jan 7, 2004
Messages
5
Re: 75hp missing after high speed runs

Thanks---what about powerhead companies-do the rebuilds really stand up like the new ones? Any recomendations? Can you say that on here?
 
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dilligafda

Petty Officer 1st Class
Joined
May 13, 2003
Messages
315
Re: 75hp missing after high speed runs

Honestly, I would look to the OEM manufacturer first. I know that Merc has a reman program, but not sure of others. We do most of our own rebuilding here so I really don't know of any aftermarket companies or what kind of work they do. Anyone else have an opinion?
 
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